Nigerian Journal of EntomologyPublished by the Entomological Society of Nigeria

www.esn.org.ngISSN: 0331-0094Volume 33,2017

Effect of Grain Characteristics of Four Local Rice (Oryza sativa L)Cultivars on Development of the Rice Weevil (Sitophilus oryzae L.)

[Coleoptera: Curculionidae] in South western Nigeria

*ADU, B.W., OGEDENGBE, A. 8., ADEYEMI, lA, AND ADEDIRE, c.o.Department of Biology, Federal University of Technology, Akure

Nig. J. Entomol. 33: 47 - 55 (2017)ABSTRACT: The effects of grain characteristics of four local rice cultivars namely, Erin-Ijesharice, lgbirno rice, Gboko rice, and Ogbese rice, on development ofthe rice weevil (Sitophilus oryzaeiwas studied under ambient laboratory conditions at 30±2°C and 75 ±5 % relative humidity at Akure,Nigeria. Complete randomized experimental design was used with four replications per treatment.Proximate and mineral composition of the grains were determined using the Official Methods of theAssociation of Analytical Chemists and Atomic Absorption Spectrophotometer, respectively.Oviposition and adult emergence of rice weevil (Sitophilus oryzaes in relation to graincharacteristics, mineral profile, and proximate composition of four rice cultivars (lgbimo rice,Ogbese rice, Erin-Ijesha and Gboko) were investigated. Highest number of eggs (69.25±0.85) laidby S oryzae was found in Erin-Ijesha rice which showed that the weevil preferred Erin-Ijesha rice toother cultivars. Highest number of adults (38.0±0.67) also emerged from Erin-ljesha rice cultivar.There was a positive significant difference (P<0.05) between the Erin-Ijesha rice and three othercultivars of rice. The lowest number of eggs (57.75 ±0.95) and the least percentage of adultemergence (28.5±0.48) laid by S oryzae was found on the Ogbese rice. The number of eggs laid andthe numbers of adult emergence were correlated with other parameters. There was a strong positivecorrelation between eggs laid and copper (r = 0.653, P <0.05) and Cd (r = O.688P< 0.055). Also, therewas a strong positive correlation between percentage of adult emergence and crude protein (r =0.608), crude fat (r = 0.676), P (r= 0.755) Pb (r= 0.787) and Cd (r = 0.905). Erin-Ijesha rice cultivarwas the most susceptible to Soryzae infestation due to high percentage of essential nutrient andmineral content, while Ogbese lice ranked least preferred rice cultivar for oviposition anddevelopment. The study has shown that grain characteristics and composition playa major role in thesusceptibility of rice grains to infestation by S orvzae.

Keywords: Sitophilus orvzae, Rice cultivars, Adult Emergence, Morphological characteristics,Nutrient content.

INTRODUCTIONRice is a vital food for both man and animal.

Almost half of the world's population,particularly in developing countries, depend onrice as the major source of nutritional calories. InAfrica, Nigeria remained the highest consumerand importer of rice (Osagie, 2014). In an effort

*Corresponding author:E-mail: bwadu@futa.edu.ng

aimed at reducing importation of this commodity,govcmment has continued to encourage massproduction of lice. This has led to cultivation oflocal varieties which are now common inNigeriamarkets. Recently, there was a collaborationbetween Lagos and Kebbi States on massiveproduction of local rice for consumption. Theoutcome was the production of "Lake Rice" anacronym derived from Lagos and Kebbi (TheGuardian, 2016). The rice has since flooded the

DOI:10.36108/NJE/7102/33(0160)

4~ • NIGERIAN JOURNAL OF El\TOMOLOGY - Volume 33. 2(}} 7

market especially in Lagos and Kebbi States,Nigeria.

One of the problems facing commercialfarming in developing countries is the post-harvest losses caused by pests such as insects,mites and rats (Odeyerni and Daramola, 2000).Among these pests, insects are the major factoras they are responsible for extensive losses ofrice grains in the field and in the store resulting

~. -in 20-40% weight loss (Subedi et. al., 2009).Rice weevil (Sifophillis oryzaei is the mostnotorious major store pest of rice (Adedire,2002). It originated from India from where itspread across the world (Hill and Waller, 1988).The adult weevil can fly and it is attracted bylight; when disturbed, adults pull in their legs,fall to the ground and feign death. The adultfemale eats a cavity, sealing in the egg withsecretions from her ovipositor. The larvadevelops within the seed, hollowing it out whilefeeding. This is a destructive activity that hascaused extensive losses of rice grains in thestore.

The destructive activities of rice weevils onrice have been strongly correlated to certainproperties of the grains like cultivar types andproximate compositions. Bamisile et al., (2014)showed that rice cultivars with high moisturecontent had higher susceptibility to S oryzaeinfestation. Similarly, Campbell (2002)showed that oviposition of S oryzae was morein rice cultivars with higher grain size than thesmall ones which may not have any significanteffect on the adult emergence. Also, Islam et 01.(2007) showed that the degree of infestation ofrice cultivars by S Ol:rzac is largely influencedby a combination of factors such as grainhardness, nutritive value and natural resistance.Although, there are studies that have shown theeffects of grain characteristics or rice cultivarson the growth and development of S 01:1':::0("

not many studies have attempted to show thecombined effects of both the grain characteristicsand ricc cultivars on growth and development ofS orvzae . This study investigated the effects ofboth the grain characteristics and proximatecomposition of four different rice cultivars onthe growth and development ofS O/} -zae.

MATERIALSAl\'D METHODS

Infested local ricc grains obtained at Erckcsanwere Market. Akure, Ondo State, Nigeria, andthe rice weevils therein sieved and used toestablish a laboratory culture. The sixtransparent culture containers with the lidsperforated and scaled with muslin cloth werekept at 28 ± 2°C and 75% ± 5% relativehumidity and the food resource replenishedconstantly. Four local rice cultivars, namelyIgbimo rice, Erin-Ijesha rice, Gboko rice, andOgbese rice, used for this study were obtainedfrom Erekesan Market, Akure. Prior to use, thegrains contained in zip lock bags weredisinfested for three days in a deep freezer at -20°e, and air-dried for one day at the centrallaboratory of Federal University of Technology,Akure. All tests were conducted in thelaboratory using complete randomize designwith four replications per treatment.

Grain Characteristics ofCultivarsTo compare grain characteristics of thecultivars, 19 sample of each was weighed on aMetler" beam balance (PB 3002), sorted intodamaged and undamaged category, and counted.Twenty grains were taken at random from each ofthe four rice cultivars from Erekesan Market,Akure then weighed; grain length and widthmeasured with Vintage Imperial" micrometerscrew gauge Model Cglp. Shape and colour ofthe grains were visually noted.

Proximate and Mineral CompositionProximate composition ofthe test cultivars wasdetermined using AOAC (1990). For mineralcomposition, 1g grain sample was ashed in amuffle furnace at 550°e, cooled in a desiccator,dissolved in lml of concentrated nitric acidafter which distilled water was added andfiltered through Whatman No. I filter paperinto a clean 250ml beaker. The filtrate wasmade lip to 50 1111 with distilled water and theconcentration of Cadmium (Cd). Copper (Cu),Lead (Ph), Phosphorus (P) and Zinc (Zn)determined using Atomic AbsorptionSpectrophotometer (Buck 210 Model 200).

Adu ('/01 .. Maize Grain Characteristics and Development of Sitophilus Orear?

Effect of Rice Cultivar on WeevilOviposition and DevelopmentFive pairs ofweevils were introduced into 50 gof grains in plastic containers covered with lidsthat had been perforated and lined inside withmuslin cloth. The containers were kept in insectbreeding wire mesh cage in the laboratory atambient conditions (27-35"C and 70-75%relative humidity). After 14 days, the weevilswere removed and the grains stained with acidfuschin and examined under the microscope tocount egg plugs following the method ofFrankenfeld (1948). The dishes were examinedfor emergence of adults. The total number ofemerged adults were expressed as a percentage ofthe number of eggs plugs counted and the numberof emergence were recorded dai Iyfor 14days.

Rearing of Test Sitophilus oryzaeThe rice weevil, Sitophilus oryzae; used for thisstudy was obtained from naturally infestedlocal rice grains obtained from ErekesanMarket, Akure, Ondo State, Nigeria. Four localrice cultivars collected from Erekesan MarketAkure, namely, Ogbese rice, Igbimo rice, Erin-Ijesha rice, and Gboko rice were used for thisstudy. The rice cultivars were each kept in ziplock bags and disinfested in a deep freezermaintained at temperature of -20°C for 3 daysand later air-dried at central laboratory of theFederal University of Technology, Akure for 24hours prior to use to avoid moldiness. The adultS. oryzae were reared in the laboratory atambient conditions ono ± 2°C and 75% ± 5%relative humidity in six transparent containerswith the lids perforated and scaled with muslincloth. The muslin cloth ensured adequateaeration of the rearing containers, preventedescape of the weevils and the entry of otherinsects. The insect culture was maintained bycontinuous replacement of damaged grainswith fresh uninfected wholesome rice grains.

Determination of MorphologicalCharacteristics of Test Rice CultivarsOne gram of each rice cultivar was weighedusing Metler" beam PB 3002 weighing balance.The total number of grains in each gram of ricewas counted, the number of broken and

• 49

wholesome grains were noted.Twentywholesomegrains were weighed separately for each ricecultivar, The length and width of each rice grainwas determined using a Vintage Imperial'micrometerscrewgauge(ModelCg1 p).

Determination ofthe Proximate and MineralComposition of Test Rice CultivarsProximate and mineral composition of thegrains were determined using the OfficialMethods of theAssociation ofAnalytical Chemistsand atomic absorption spectrophotometer,respectively. The nutrient content of each of thefour lice cultivars (e.g., crude protein, moisture,fat, ash and crude fibre, and gross energy) wereassayed using the Official Methods of theAssociation of Analytical Chemists (AOAC,1990).This was done purposely to determine their(i.e. nutrient content) influence on the growth ofS.oryzae.

Mineral content analyses were canied out onall the samples as follows: One gram (lg) of eachsample was ashed in a muffie furnace at 550°C.The ash sample and dishes were removed andtransferred into the desiccator to cool after whichthe samples were dissolved with 1ml ofconcentrated nitric acid. Distilled water wasadded and filtered into a clean 250ml beakerusing Whatman No. I filter paper. Distilledwater was later used to dilute the solution up to50ml. Atomic absorption spectrophotometerBuck 210 Model 200 was used to determineconcentration of the elements namely Lead.(Pb), Zinc (Zn), Cadmium (Cd), Copper (Cu),and Phosphorus (P).

Determination of the Effect of Host Cultivaron Oviposition and Adult Emergencefifty grams of each rice media were weighedinto separate plastic containers and replicatedfour times. Ten pairs (10 cJ: 10 9) of S. orvzaewere introduced into the plastic containers andcovered with the lid that had been perforatedand covered on the inside with muslin cloth.The containers were then kept in insectbreeding wire mesh cage in the laboratory atambient temperature (30 ± 2°C) and relativehumidity (75% ± 5%), they were then removedafter 14 days. Oviposition was determined by

50 • NIGERIAN JOURNAL OF ENTOMOLOGY - Voltune 33.2017

counting the eggs laid under the microscopeafter staining with Acid Fuschin followinu the~ ~experimental protocol ofFrankenfcld ( I948).

Another separate experiment involving 10pairs (100': 109) similarto the one for ovipositionwas set up. The insects were allowed to copulateand lay eggs for 14days afterwhich the adults wereremoved. Thereafter, adult emergence wasmonitored daily for 14 days after the first day ofemergence.

DataAnalysisAll data obtained were ana lysed using analysisof variance ANOYA and the means wereseparated using Tukey's post hoc test. Pearsoncorrelation analysis was used to determine therelationship between oviposition and adultemergence (independent variables) and graincharacteristics, proximate and mineralcomposition (dependent variables).

RESULTS

Grain Characteristics of Rice CultivarsThe morphological characteristics of the fourrice cultivars are presented in Table 1.The grainweight was significantly higher in Ogbese rice(0.23 g) compared to Erin-ljesha(O.03 g), Gboko(0.04 g) and Igbimo (0.04 g) rice cultivars wherethe grain weight did not differ significantly.

There was no significant difference in grainlength among the four rice cultivars althouuh'-- (.... ~Ogbcsc rice (5.63mm) seemed to be marginallylonger than the other three cultivars. Similarly,the grain width did not differ significantlyamong the tour rice cultivars considered in thisstudy. The mean number of wholesome grainsdiffered significantly among the cultivars withErin-Ijesha and Ogbese rice having the highestmean number of wholesome grain (42.75 and40.75 respectively) while the mean number ofwholesome grain were statistically the same forGboko and Igbimo rice (30.00). The highestmean number of broken grains was recorded inOgbese rice (10.75) while Igbimo rice had thelowest mean number of broken grain (1.50).The Ozbese and Izbimo rice cultivars both had~ ~dull white grain colour while on the other handthe Erin-Ijesha and Gboko rice cultivars bothhad light brown grain colour.

Proximate Composition of Test RiceCultivars Infested withS. oryzaeThe proximate composition of the four ricecultivars are shown in Table 2. Generally, therewere significant differences in the proximateparameters across all the rice cultivars. Erin-Ijesha rice had the highest protein content(7.88%) while Ogbese rice had the lowestprotein content (7.18%). The fat content was

Table I: Comparison of the grain characteristics of the four local rice cultivars

Grain Grain Grain Number of Number ofRice cultivars weight (g) length (mm) width( 111m) wholesome broken grain Colour

Ogbese O.23h±O.OO 5.6"±O.00 0.R6"±O.OI 40.7S"± 1.3R 10.7Sh±2.69 dull whiteGboko 0.04"±0.OO 5.54"±0.OR O.85"±O.OI 30.00"± 1.08 2.00"±0.71 light brownErin-Ijesha 0.03"±O.OO S.4S"±O.OS O.86"±0.0 I 42.75h±O.85 1.50"±O.96 light brownIgbimo O.04"±0.OO 5.54"±O.OS O.86"±O.OI 30. 00" ±0.65 1.75"±O.63 dull white

Column means followed by the same letter are not significantly different (P>O.05) by Tukey test

Table 2: Proximate composition (mean 'Yt, ± SE) of the four local rice cultivars

Crude Ash Carbohydrate Gross EnergyRice culuvars Protein Crude Fat Ash Fibre Content Moisture content (kcal,'g)

Ogbese 7. I S'±O.OO 3 .22'±o.o I 4.44"±O.OI 4.27"",,()() I 11.38"±O.OO 69.51"±O.OO 3.21"±O.OOGboko 7 .44h±O.O I 3.4Xh±OOO 4.57"±O.OO 3.84"±O.O() 11.5~d±O.(l1 69. I S"±O.OO 3.83h±O.OOErin-Ijesha 7.8X"±().OO 3.94dJ.().O I 5. 95d±().O I 4.44'~·O.00 10.65"::10.01 ()7.14h:Hl.O I 394dJO.OOlgbimo 7.87'±O.OO 3.l·W±O.OO 5.77'±O.O I 4.27"±0.O I 11.04 b±O.O I 67.21"±O.OI 3.86"±O.OO

Column means followed by the same letter are not significantly different (P>0.05) by Tukcy rest

Adu e: al.. Maize Grain Characteristics and Development or Sitophilus Orvzae

highest in Erin-Ijesha rice (3.94'%) whileOgbese rice bad the lowest fat content (3.nt;,/o),The Frin-ljcsha rice had the lowest moisturecontent (10.65%) while Gboko rice had thehighest moisture content (I 1.51%). Fibrecontent was lowest in Ogbesc rice (4.49%) andhighest in Erin-Ijesha rice (5.95%), The ashcontent was higher in Erin-Ijcsha rice (5.9S'%)compared to other rice cultivars where the ashcontents were 4.44%. 4.57% and 5.77% forOgbese, Gboko and Igbimo rice respectively. Thepercentage carbohydrate was significantly higherin Ogbcse (69,51) and Gboko (69.IS) licecompared to Erin-Ijesha (67.14) and Igbimo(67.21) lice. The highest gross energy wasrecorded in Erin-ljesha lice (3 .94kcai/g) while thelowest was recorded in Ogbese rice (3 ,21 kcal/g).

l\ lineral ContentThe levels of Pb. Cd, Zn, Cu and P in the grainsare shown in Table 3. The highest amount ofPb'was recorded in Erin-Ijesha rice (0.053~g/g)while the lowest was recorded in Ogbese rice(0.044~g/g). Gboko rice had the highest amountof Cd (0.031 ug/g) while Ogbese rice had thelowest (0.0 18~lg!g). The amount of Zn in thegrains differed significantly among the cultivarswith the highest in Ogbese rice (9.32~g/g) andthe lowest in Erin-Ijesha rice (7. 91 ug/g). Igbimorice had the highest amount of Cu (1.85pg/g)

• 51

while Gboko rice had the lowest] 1.58pg/g). Thehighest amount of P was detected in Erin-Ijesharice (0.345) while the lowest amount of P wasdetected in Ogbese rice (0.3 12pg/g).

Oviposition and Adult Emergence ofSitophilus oryzaeThe mean number ofeggs laid by S. 01:1'::0(> andpercentage adult emergence on the four ricecultivars are presented in Table 4. Erin-Ijesharice had the highest mean number of eggs(69.25) while the lowest "vas observed inOgbcse rice (57.75). The rice cultivars wereobserved after oviposition for a period of 30days after infestation, no emergence ofweevilwas recorded during this period. On the 54thday after infestation, adult emergence wasobserved. Erin-ljesha rice had the highest meanpercentage of adult emergence (38.0), whilethe lowest was recorded in Ogbese rice (28.5).The daily and the cumulative emergence ofs.oryzae from the four rice cultivars arepresented in Figures 1 and2 respectively.

Correlation ofWeevil Oviposition and Emergencewith Grain Characteristics, Nutrient andMineral Composition of Rice GrainsThe correlation matrix between adult emergence,oviposition and mineral/proximate compositionsare shown in Table 5. There was a strong positive

Table 3: Mineral content (Mean I1g/g ± SE) of the four local rice cultivars

Rice~lg/g

cultivars Lead (Pb) Cadmium (Cd) Zinc (Zn) Copper (Cu) Phosphorus (P)

( )gbese 0,0-+-+"+0,00 O,OI8"+O.()O 9.32,5"-1O.()I 1.73()'+O.OI 0.312"+0.00Gboko O,O-+6"h±O,OO 0.031 d::!cO,OO ~.7-+0':±:O.OI 1,585'1+0.00 0.325"±0.00Erin-Ijcsha o ,OS3l:±-O.00 o.ozs-io.oo 7.915'1+0,0 I 1,6xol'+o.oO O.3-+Su:fO.OOlgbimo ()O-+xh1().OO o.o2i':10,()() 8,21 Oi'+O.OI 1.855ci+O(JO 0,337 c±O.OOColumn means followed by the same letter arc not significantly different (P 'CL():,) by Tukcy test

Table -1-:!\ lean (± SE) numher of eggs laid and adult elllergence b~ ,\'ifoplrilllS O1:I'';,aC on riel' ctllth'ars

Rice cultivars Number of eggs laid °0 adult emergence

OgbcseGbokol.rin-ljcshnlgbimo

S 7 ,7:' ;I.U1.9:'() I.OOb±O.,57()L),2:,d!()~5

64,25L±O,57

2~,:"1±0.4~295b+0.573~.()d±(J.() 736.0"±0.54

Column means followed by the same letters arc not signiric:ll1tly different (P>OJ)5)

52 • l\ICiERIAN JOURNAL Or ENTOi'-10LOGY - I ()/11117!.' 33, un :

'"

1 '; 1 ) 1,1"

Figure I: Mean daily adult emergence of S. OI:rzae from four rice cultivars

if:

"i, ,I',

Figure 2: Cumulative adult emergence of S. oryzae from four rice cultlvars

1. (,

Adu CI al.. Maize Grain Characteristics and Development ofSifOpliillls Orvcae •

Table 5: Con-elation of grain characteristics, number of eggs laid and adult emergence of SitophilusOITZ{{C with proximate composition and mineral content of the local rice cultivars

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n.:-;~.. ..: .fI.;jI~ -il.-l:: .li.(·2<) " 755 {I.~n...: Ii ~I-'J;: IJ.~.i~: il .J ~ i..J _11.;-0:-' :.I.--=:.••} iI.9_N 0.":':., JI <~<;.; 0.1 -" iJ111I)

correlation between percentage adult emergenceand crude protein (r = 0.608), crude fat (r =0.676), crude fibre (1'= 0.50 1), Pb (1'=0.787), Cd(r = 0.905) and P (r = 0.755) while a negativecorrelation was observed between percentageadult emergence and ash content (r = 0.506), Cu(1'= 0.748) andZn (r= 0.514). There was a strongpositive correlation between mean number of eggslaid and Cd(r=0.688) andCu(r=0.653) while therewas a negative correlation between mean number ofeggs laid and crude protein(r=0.658), crude fat (r=O.(32)and P(r=0.629).

DISCUSSIONThe morphological characteristics of the fourrice culiivars investigated in study showed thatOgbesc rice had the highest number of brokengrain, least number of eggs laid and the leastpercentage of ad lilt emergence. Grain size havethe potent: a I ofdctcrrn ini ng the number of eggsthat the grain can contain (Cambpcll. 20(2).Eri n-Ijcsha rice cui tivar had the least number ofbroken grains hut the highest number ofwholesome grains. The rice cultivar (Erin-ljcsha) a Iso had the highest number of eggs laid,since it was the rice cultivar with highestsizet Cambpell. 20(2). The rice cultivar likewisehad highest percentage of adult emergence

which showed that Sioryzae have preferencefor wholesome grain than on broken gram(Coombs and Woodroff, 1965).

The moisture content of any food is anindex of its water activity and it is used as ameasure of stability and the susceptibility tomicrobial contamination (Okaraonye andIkewuchi, 2009). Wilkin and Stenning (1989)also stated that the vulnerability of grain tobiodeterioration by its own metabolic activityor by the action of insects is related to itsmoisture content. Moisture content above 16%increases enzyme activity while moisturecontent below 15% promotes little metabolicactivity that support grain viability. Makanjuolaet (1/ .• (2009) reported that the low moisturecontent of rice was a likely factor that increasedsusceptibility of rice cultivars in storage to SO!l'Z(/(! infestation. The moisture contentsrecorded for all the rice varieties used in thisstudy were lov, enough to support the growth ofthe rice weevi L Sitophilus OIT::OL'. The numberDr adults reduced as the development periodprogressed because there was no replenishmentofthe fond media.

There was a strong positive correlationbetween percentage adult emergence and crudeprotein and a negative correlation was observed

54 • NIGERI.-\l\ JOURN:\L OF El\TUMOLOGY - I ()/UIl1e' 33, ]()/!

between percentage adult emergence and ashcontent. Erin-Ijcsha rice cultivars producedhigher number of eggs and higher percentageof adult emergence because of higherpercentage of crude protein, crude fat, andcross encruv that characterized the rice grain,"-~. "- .

The least percentage of adult emergence wasfound on Ogbesc rice cultivar which was ricecultivar with the least percentage of crudeprotein, and crude fat. Ogbese rice however hadthe highest percentage of carbohydrate whichmay not meaningfully have significant effect oneggs and larvae development. This study hadshown that high nutrient and presence ofessential mineral content in rice cultivarscontribute to rapid development of immaturestagesofrice pests (Shah et al., 20 15),

The mean levels of Cd and Pd differed amongthe four rice cultivars with Ogbese lice having theleast mean concentration of lice cultivars, Thevalues measured for Cd and Pb for all the ricecultivars were found to be lower than what wasmeasured in a previous study carried out inNigeria (Ihedioha et al., 2013 and Adedire et al..2015). The values obtained in this study alsosignificantly differed from the reference values setby Codex Alimentarius Commission. Forinstance, the reference value for Cd is 0.05 ug/gwhile that ofPb is 0.2 ug/g (CAC 20 II:Hao et a/20 II). The difference in concentration level of Cdcould be as a result of different concentrations oftheCd and Pb in the soil (Parisa etal., 20 13).

General decrease in mineral content of allthe rice cultivars can also be attributed tomilling, since milling and polishing are widelyknown to decrease mineral contents of ricegrain (Rivero et 01., 2007). Oko et 0/., (2012)also agreed that more than half of phosphorousand other minerals in rice arc removed duringmilling. The concentration of chemicals in thesoi Iwhere the rice is being cu ltivatcd a lso playedimportant role in the determination of chemicallevels of minerals in the rice grain. For instance,10\,,' concentration of mineral clements in the soilwill bring about low concentration ofthe mineralelement in plant (e.g. rice) growing on the soil.which is responsible for low mineral contentsof rice cultivars under investigation (Robson,1993).

In conclusion, Erin-ljesha rice was the mostsusceptible to S.()/T~OC infestation followedclosely by Gboko rice and lgbimo rice. whilethe least susceptible was Ogbese rice. Thus. it isevident that varietal resistance could be the keyin stored rice as storage losses are becomingmore serious amongst countries trying toachieve self-sufficiency in quality and quantityproduction of cereals. Emphasis should beplaced on the utilization of naturally resistantcultivars of staple foods. Moisture content ofstored produce needs to be adequately monitoredand controlled due to the fact that it plays a majorrole in supporting the growth and developmentof storage insects. Host plant resistance to riceweevil is also a potential means ofreducing post-harvest losses of stored rice and it is thereforerecommended.

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ISSN:0331-0094volume _,3. :'017[1[147-55

DOI:10.36108/NJE/7102/33(0160)